The present invention pertains to powered orthotic systems and, more particularly, to fail-safe joints for powered orthotic systems.
Orthotic systems, such as human exoskeleton devices, are being used to restore, rehabilitate, enhance and protect human muscle function. These exoskeleton devices are systems of motorized braces that apply forces to the appendages of an exoskeleton user. In order to enhance exoskeleton device safety, exoskeleton devices often include a number of fail-safe systems (i.e., systems that fail in a safe state). One such fail-safe system is a normally engaged brake that is positioned in a joint between exoskeleton braces. These normally engaged brakes are used in exoskeleton joints in which a locked relative movement configuration is preferred over a free relative movement configuration during a failure.
The primary disadvantage of normally engaged brakes in exoskeleton devices is that the normally engaged brake prevents a user from adjusting the exoskeleton device without the use of active controls. Particularly during a control system failure, a normally engaged brake will lock the exoskeleton in its current position and prevent the user from adjusting the exoskeleton until the failure has been corrected and the control system resumes proper operation. Moreover, users cannot move the exoskeleton joints when the device is powered off, leading to great inconvenience during donning, doffing, sizing, transport and storage of the device even when there is no failure. With the above in mind, there is considered to be a need in the art for an exoskeleton device with a fail-safe system that eliminates or mitigates these problems by allowing a user to adjust the exoskeleton device during a control system failure or when the device is powered off.